Network management server and recovery method

ABSTRACT

A network management server stores, in terms of a transmission path within the network, each occurrence pattern of a failure occurrence area in which a failure has occurred in a communication apparatus through which the transmission path passes. Information for identifying a recovery plane serving as a set of recovery paths corresponding to each occurrence pattern and information for identifying the communication apparatus through which each of the recovery paths passes is also stored. When a failure occurs in any one of the plurality of areas, whether or not the failure corresponds to any one of the failure occurrence patterns, the information for identifying the recovery plane corresponding to the identified failure occurrence patterns is acquired; and the communication apparatus through which each of the recovery paths included in the recovery plane passes is notified of the information for identifying the recovery plane acquired.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2013-236808 filed on Nov. 15, 2013, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

This invention relates to a network management server for managing anetwork and a recovery method therefor.

Background arts of this technical field include JP 2013-46322 A, JP2013-85061 A, and WO 2010/018755 A1. In the technology disclosed in JP2013-46322 A, a network management system includes a plane managementtable for managing a transmission plane defined as a set of transmissionpaths within a transmission network. Further, the plane management tablesets and manages not only a transmission plane (active plane) applied ata normal time but also at least one transmission plane (standby plane)applicable when a failure occurs in the transmission network. When afailure occurs in the transmission network, the network managementsystem changes an applied plane to an appropriate transmission plane.

In the technology disclosed in JP 2013-85061 A, respective communicationapparatus are classified into a plurality of areas, each of whichincludes an edge node through which an active path first passes and anedge node through which the active path last passes. The networkmanagement apparatus holds failure information including a valueindicating whether or not a failure has occurred in each area, and alsoholds alternative path information including a value indicating aplurality of edge nodes, a value indicating an alternative area of eacharea, and a priority assigned to each alternative area. When it isdetermined that the failure has occurred in a first area based on thefailure information, the network management apparatus identifies thealternative area of the first area based on the alternative pathinformation. When it is determined that the failure has not occurred inthe alternative area of the first area, the network management apparatusdetermines the alternative area of the first area as a second areathrough which the active path passes, determines two edges nodesincluded in the second area based on the alternative path information,and detects each communication apparatus through which the active pathbetween the two edge nodes passes.

In the technology disclosed in WO 2010/018755 A1, a path generationmodule generates in advance standby path information to be used when afailure occurs based on predicted topology information and predictedresource information, which are changed in accordance with a predictedfailure site. The path generation module stores the generated standbypath information in a data storage unit. A path information notificationmodule of a transport control server (TCS) (S-1) notifies a node N ofgenerated normal path information. A failure information acquisitionmodule of the TCS (S-1) detects an occurrence of a failure. When thefailure information acquisition module detects the occurrence of afailure, the path information notification module notifies the node N ofthe standby path information stored in the data storage unit.

However, in the technology disclosed in JP 2013-46322 A, when a failurehas occurred in a specific set path, it is determined whether or not thepath is available, for all the paths that pass through a plurality ofrelay points in the standby plane, and the standby plane affected leastby the failure is selected based on the priorities of the respectivepaths. Therefore, it is necessary to execute a considerable amount ofprocessing from the detection of the failure in the set path until thedetermination of the standby plane for recovery. Accordingly, it is moredifficult to apply the technology to a communication system having alarger scale.

In the technology disclosed in JP 2013-85061 A, when a failure isdetected in the area to which the communication apparatus belongs,already-set path settings for the paths passing through the area thathas caused the failure are abolished one by one in order, and then pathsettings as bypasses are enabled. Therefore, it is necessary to executea considerable amount of processing until all the already-set paths arerecovered, and because the bypasses are determined and set one by one,the path settings optimal as a whole cannot be executed. Accordingly, itis more difficult to apply the technology to a communication systemhaving a larger scale.

In the technology disclosed in WO 2010/018755 A1, the standby pathinformation to be used when a failure occurs is calculated in advance,and each node is notified of different standby path information or adifferent ID indicating the path information. Therefore, when a largenumber of nodes exist, it is necessary to notify each node of anenormous number of different pieces of path information or necessary toestablish coupling to the large number of nodes to be notified andnotify the nodes of the large number of different IDs, which imposes aheavy load on the side that notifies of the path information ornecessitates much time for the notification. Accordingly, it is moredifficult to realize quick recovery for a communication system having alarger scale.

SUMMARY OF THE INVENTION

It is an object of this invention to realize reduction of load requiredfor setting for quickly recovering an existing set path when a failureoccurs in a communication system.

An aspect of the invention disclosed in this application is a networkmanagement server to be coupled to communication apparatus withinrespective areas of an area group forming a network, the networkmanagement server comprising: a processor for executing a program; amemory for storing the program to be executed by the processor; aninterface for controlling communications to/from each of thecommunication apparatus; and a storage for storing data, wherein: thestorage stores, in terms of a transmission path within the network, foreach occurrence pattern of a failure occurrence area in which a failurehas occurred in the communication apparatus among a plurality of areasthrough which the transmission path passes: information for identifyinga recovery plane serving as a set of recovery paths corresponding to theeach occurrence pattern; and information for identifying thecommunication apparatus through which each of the recovery paths passes,in association with each other; the communication apparatus each storerecovery information comprising: information for identifying therecovery plane serving as the set of recovery paths passing through anown apparatus; and information for designating coupling counterparts towhich the own apparatus is to be coupled in each of the recovery pathspassing through the own apparatus; and the network management serverexecutes: an identification procedure of identifying, when a failureoccurs in any one of the plurality of areas, whether or not the failurecorresponds to any one of failure occurrence patterns; an acquisitionprocedure of acquiring the information for identifying the recoveryplane corresponding to the one of failure occurrence patterns identifiedin the identification procedure from the storage; and a notificationprocedure of notifying the communication apparatus through which each ofthe recovery paths included in the recovery plane passes of theinformation for identifying the recovery plane acquired in theacquisition procedure.

According to the exemplary embodiment of this invention, load requiredfor setting for quickly recovering an existing set path when a failureoccurs in a communication system can be reduced. Other objects,configurations, and effects than those described above are clarified bythe following description of an embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram illustrating a system configurationexample of a communication system according to the first embodiment.

FIG. 2 is an explanatory diagram illustrating a system configurationexample of a communication system after the failure recovery accordingto the first embodiment.

FIG. 3 is a sequence diagram (first half) illustrating a flow of thefailure recovery according to the first embodiment.

FIG. 4 is a sequence diagram (second half) illustrating a flow of thefailure recovery according to the first embodiment.

FIG. 5 is an explanatory diagram showing a storage content example of arecovery plane list table.

FIG. 6 is explanatory diagram showing a storage content example 1 of apath coupling setting table showing the coupling relations between thetransmission apparatus for each recovery plane.

FIG. 7 is explanatory diagram showing a storage content example 2 of apath coupling setting table showing the coupling relations between thetransmission apparatus for each recovery plane.

FIG. 8 is explanatory diagram showing a storage content example 3 of apath coupling setting table showing the coupling relations between thetransmission apparatus for each recovery plane.

FIG. 9 is explanatory diagram showing a storage content example 4 of apath coupling setting table showing the coupling relations between thetransmission apparatus for each recovery plane.

FIG. 10 is explanatory diagram showing a storage content example 1 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 11 is explanatory diagram showing a storage content example 2 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 12 is explanatory diagram showing a storage content example 3 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 13 is explanatory diagram showing a storage content example 4 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 14 is explanatory diagram showing a storage content example 5 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 15 is explanatory diagram showing a storage content example 6 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 16 is explanatory diagram showing a storage content example 7 of arecovery path setting list table for each recovery plane correspondingto each transmission apparatus.

FIG. 17 is a block diagram illustrating a hardware configuration exampleof the network management server according to the first embodiment.

FIG. 18 is a block diagram illustrating a functional configurationexample of the network management server according to the firstembodiment.

FIG. 19 is a flowchart illustrating a processing procedure example ofthe calculation of a failure recovery plane and recovery planeinformation notification to the respective communication apparatus thatare executed by the network management server according to the firstembodiment.

FIG. 20 is a flowchart illustrating a detailed processing procedureexample of recovery path calculation processing executed by the networkmanagement server according to the first embodiment.

FIG. 21 is a flowchart illustrating a detailed processing procedureexample of the monitor of the failure and recovery plane notificationthat are executed by the network management server according to thefirst embodiment.

FIG. 22 is a block diagram illustrating a hardware configuration exampleof the communication apparatus according to the first embodiment.

FIG. 23 is an explanatory diagram illustrating a system configurationexample of the communication system according to the second embodiment.

FIG. 24 is an explanatory diagram illustrating a system configurationexample of the communication system after the failure recovery accordingto the second embodiment.

FIG. 25 is a sequence diagram (first half) illustrating a flow of thefailure recovery according to the second embodiment.

FIG. 26 is a sequence diagram (second half) illustrating a flow of thefailure recovery according to the second embodiment.

FIG. 27 is a flowchart illustrating a processing procedure example ofthe calculation of the failure recovery plane and the recovery planeinformation notification to the respective area management servers thatare executed by the network management server according to the secondembodiment.

FIG. 28 is a flowchart illustrating a processing procedure example ofthe monitor of the failure and recovery plane notification that areexecuted by the network management server 9 according to the secondembodiment.

FIG. 29 is a flowchart illustrating a processing procedure example ofprocessing in which the area management servers notify the respectivecommunication apparatus of the recovery path according to the secondembodiment.

FIG. 30 is a flowchart illustrating a processing procedure example of afailure monitor processing operation executed by the area managementserver according to the second embodiment.

FIG. 31 is a flowchart illustrating a processing procedure example forthe path recovery within the area according to the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of this invention is described by taking an examplein which an entire network is partitioned into a plurality of areas anda failure is managed in units of areas to quickly recover a settransmission path at an occurrence of a failure. Further, the firstembodiment is described by taking an example in which a communicationsystem forms a packet transport network.

<Network Configuration Example>

FIG. 1 is an explanatory diagram illustrating a system configurationexample of a communication system according to the first embodiment. Thecommunication system according to the first embodiment includes anetwork management server 9, communication apparatus 11 to 14, 21 to 24,31 to 34, 41 to 44, 51 and 52, 61 and 62, 71 and 72, and 81 and 82, andterminals 101 to 104, to form a network. It should be noted thatservers, other communication apparatus, or networks may be employedinstead of the terminals, but this example is described by taking theterminals as an example. It should be noted that the communicationapparatus and the terminals (including servers) are collectivelyreferred to as “transmission apparatus”. Further, in FIG. 1, for thesake of convenience, the network management server 9 is coupled only tothe communication apparatus 72, but is also coupled to othercommunication apparatus.

In the first embodiment, the communication apparatus 11 to 14 form anarea “1”, the communication apparatus 21 to 24 form an area “2”, thecommunication apparatus 31 to 34 form an area “3”, the communicationapparatus 41 to 44 form an area “4”, the communication apparatus 51 and52 form an area “5”, the communication apparatus 61 and 62 form an area“6”, the communication apparatus 71 and 72 form an area “7”, and thecommunication apparatus 81 and 82 form an area “8”.

Further, in the first embodiment, a transmission path P1 (passingthrough the terminal 101, the communication apparatus 14, 11, 51, 61,62, 71, 31, and 34, and the terminal 103) and a transmission path P2(passing through the terminal 102, the communication apparatus 23, 22,62, 71, 72, 82, 42, and 43, and the terminal 104) are set at anoperation start stage.

The network management server 9 calculates in advance, for a settransmission path, a recovery path to be used when a failure occurs inunits of areas. In the first embodiment, eight areas exist, and hencethe number of failure occurrence patterns in units of areas is 2⁸=256.There are one state in which a failure has occurred in none of theareas, eight states in which a failure has occurred in a given one area,twenty-eight states in which failures have occurred in given two areas,fifty-six states in which failures have occurred in given three areas,seventy states in which failures have occurred in given four areas,fifty-six states in which failures have occurred in given five areas,twenty-eight states in which failures have occurred in given six areas,eight states in which failures have occurred in given seven areas, andone state in which failures have occurred in all the areas.

The network management server 9 assigns an identifier (referred to as“recovery plane ID”) for identifying a recovery plane to every failurepattern, and calculates the recovery path for an active-system path setat the operation start stage as shown in FIG. 5. The recovery planerepresents a transmission plane defined as a set of recovery pathswithin the network. Further, the network management server 9 calculatesa recovery setting for paths (recovery plane) indicating couplingrelations between transmission apparatus which form the recovery planecorresponding to an area failure pattern as shown in FIG. 6 to FIG. 9.In addition, the network management server 9 calculates a recoverysetting for a path (recovery plane) for each transmission apparatus, andnotifies each apparatus of a table obtained by the calculation as shownin FIG. 10 to FIG. 16. Each transmission apparatus holds the receivedtable for path recovery for each recovery plane.

After notifying each transmission apparatus of a recovery path settingtable for each recovery plane, the network management server 9 monitorswhether or not a failure has occurred in a communication apparatuswithin the communication system. Then, the network management server 9determines whether or not a failure has occurred in units of areas,selects the recovery plane corresponding to the determined failurepattern, and notifies each transmission apparatus of the same recoveryplane ID for set path recovery. In the first embodiment, the same ID forthe identified recovery plane is transmitted to all the transmissionapparatus relating to failure recovery, and hence the network managementserver 9 does not need to notify the individual transmission apparatusof different pieces of information.

Therefore, for example, with a multicast network for management controlbuilt between the network management server 9 and all the transmissionapparatus, the network management server 9 can instruct the entirecommunication system to recover by transmitting the recovery plane IDfor the failure recovery for one time. When a failure occurs, therespective transmission apparatus perform the recovery setting for theset path in accordance with the recovery plane ID notified of by thenetwork management server 9, and execute transmission of the receiveddata.

FIG. 2 is an explanatory diagram illustrating a system configurationexample of a communication system after the failure recovery accordingto the first embodiment. The network management server 9 illustrated inFIG. 2 monitors whether or not a failure has occurred in all thecommunication apparatus within the communication system, and monitorswhether or not a failure has occurred in units of areas. The firstembodiment is described by taking as an example of a case where failureshave occurred in the area “2” and the area “6”. When a large-scaledisaster occurs or in other such case, it is assumed that a plurality ofareas are damaged substantially simultaneously. The first embodiment isdescribed on the assumption of such a case, in other words, a case wherefailures have occurred in two areas with a slight time differencetherebetween.

The network management server 9 monitors the operations of thecommunication apparatus 61, 62, 21, 22, 23, and 24 illustrated in FIG.2, and when the operations of those communication apparatus are notconfirmed, determines that failures have occurred in the area “2” andthe area “6”. It should be noted that in the first embodiment, theoperation of the communication apparatus is monitored to determinewhether or not a failure has occurred in the communication apparatus andthe area, but a link for coupling the communication apparatus to eachother may be subjected to failure monitor, to thereby determine whetheror not an area failure has occurred based on a link failure in at leastone link coupled to another area.

In the first embodiment, the network management server 9 detectsfailures in the area “2” and the area “6”, selects the recovery planecorresponding to those area failures, and notifies the transmissionapparatus within the communication system of the recovery plane ID fornotifying of the recovery plane. The multicast network is used as thenetwork for the management control, and all the transmission apparatusare notified of the same ID for recovery. It should be noted that onlythe transmission apparatus related to the recovery plane may beindividually notified of the recovery plane ID without using themulticast network as the network for the management control. This allowsthe transmission apparatus related to the recovery plane to beidentified with ease.

In the first embodiment, in which it is assumed that failures haveoccurred in the area “2” and the area “6”, the network management server9 notifies the communication apparatus 51, 52, 81, 32, and 31, theterminal 102, and the communication apparatus 13, 12, 11, 51, 52, 81,and 82 of the ID indicating the recovery plane. The transmissionapparatus that has received the recovery plane ID carries out thefollowing setting change.

The communication apparatus 51 switches the coupling of the transmissionpath P1 from the communication apparatus 61 to the communicationapparatus 52. The communication apparatus 52 transmits the data receivedfrom the communication apparatus 51 to the communication apparatus 81.The communication apparatus 81 transmits the data received from thecommunication apparatus 52 to the communication apparatus 32. Thecommunication apparatus 32 transmits the data received from thecommunication apparatus 81 to the communication apparatus 31. Thecommunication apparatus 31 transmits the data received from thecommunication apparatus 32 to the communication apparatus 34. Thetransmission path P1 is switched in the above-mentioned manner from thetransmission path P1 set at a communication system start stage, tothereby couple the terminal 101 to the terminal 103 through thecommunication apparatus 14, 11, 51, 52, 81, 32, 31, and 34. It should benoted that, although not shown, the same setting is applied to acommunication in a reverse direction from the terminal 103 to theterminal 101.

Further, the terminal 102 switches the coupling of the transmission pathP2 from the communication apparatus 23 to the communication apparatus13. The communication apparatus 13 transmits the data received from theterminal 102 to the communication apparatus 12. The communicationapparatus 12 transmits the data received from the communicationapparatus 13 to the communication apparatus 11. The communicationapparatus 11 transmits the data received from the communicationapparatus 12 to the communication apparatus 51. The communicationapparatus 51 transmits the data received from the communicationapparatus 11 to the communication apparatus 52. The communicationapparatus 52 transmits the data received from the communicationapparatus 51 to the communication apparatus 81. The communicationapparatus 81 transmits the data received from the communicationapparatus 52 to the communication apparatus 82. The communicationapparatus 82 transmits the data received from the communicationapparatus 81 to the communication apparatus 42. The transmission path P2is switched in the above-mentioned manner from the transmission path P2set at the communication system start stage, to thereby couple theterminal 102 to the terminal 104 through the communication apparatus 13,12, 11, 51, 52, 81, 82, 42, and 43. It should be noted that, althoughnot shown, the same setting is applied to a communication in a reversedirection from the terminal 104 to the terminal 102.

As described above, the failure monitor is performed in units of areasby the network management server 9, and when a failure occurs in thearea being monitored, the recovery plane ID for recovering from thefailure is notified of, to thereby allow quick recovery from thefailure.

It should be noted that the first embodiment is described by assumingthat the same network is used for all the coupling networks, but thenetwork coupling between the terminal and the area may be set to differin type from the network coupling between the areas. For example, thenetwork coupling between the areas may be a multi-protocol labelswitching-transport profile (MPLS-TP) network, while the networkcoupling between the terminal and the communication apparatus within thearea may be an Internet protocol (IP) network.

<Failure Recovery Sequence Example>

FIG. 3 is a sequence diagram (first half) illustrating a flow of thefailure recovery according to the first embodiment. The networkmanagement server 9 receives a path setting input from a networkadministrator or the like (Step S201). The network management server 9calculates the set path for each of the communication apparatus to beoperated as an active system in accordance with the input path setting(Step S202). The network management server 9 notifies the communicationapparatus and the terminal existing within each area of the calculatedpath setting for each of the communication apparatus, and executes thesetting of the path to be operated as the active system (Steps S203-1 toS203-9).

It should be noted that in the setting of the transmission path P1 andthe transmission path P2 illustrated in FIG. 1, the transmissionapparatus relating to a transmission path setting are notified of thetransmission path setting. Specifically, in the setting of thetransmission path P1, the communication apparatus 14, 11, 51, 61, 62,71, 31, and 34 and the terminals 101 and 103 are notified of the pathsetting. Further, in the setting of the transmission path P2, thecommunication apparatus 23, 22, 62, 71, 72, 82, 42, and 43 and theterminals 102 and 104 are notified of the path setting.

Subsequently to Step S203, the network management server 9 executescalculation of the recovery plane formed of a path list for recoveringthe active-system path for each area failure pattern (Step S204). Itshould be noted that in the first embodiment, the calculation of therecovery plane is performed for all the conceivable area failurepatterns, but may be performed only for the failure pattern of aspecific area.

Subsequently to Step S204, the network management server 9 calculatesrecovery path setting data for each recovery plane from the calculateddata on the recovery plane for each area failure pattern (Step S205). Anexample of calculation results thereof is as shown in FIG. 6 to FIG. 8.Subsequently to Step S205, from the calculated recovery path settingdata for each recovery plane, the network management server 9 calculatesthe recovery path setting data for each transmission apparatus and foreach recovery plane (Step S206). An example of calculation resultsthereof is as shown in FIG. 10 to FIG. 16.

FIG. 4 is a sequence diagram (second half) illustrating a flow of thefailure recovery according to the first embodiment. Subsequently to StepS206, the network management server 9 notifies the respectivetransmission apparatus of the recovery path setting data for eachrecovery plane calculated in Step S206 (Steps S207-1 to S207-9).Subsequently to Step S207, the network management server 9 starts thefailure monitor in units of areas (Steps S208-1 to S208-8). In themonitor of the area performed in Step S208, when detecting that theoperations of the communication apparatus within the area “2” and thearea “6” have stopped, the network management server 9 determines thatfailures have occurred in the area “2” and the area “6” (Step S209). Itshould be noted that in the first embodiment, it is determined that anarea failure has occurred by detecting that the operations of all thecommunication apparatus within the area have stopped, but it may bedetermined that the area failure has occurred when detecting that theoperation of at least one communication apparatus within the area hasstopped. Further, in the first embodiment, it is determined that afailure has occurred in the area based on whether or not the operationof the communication apparatus has stopped, but the failure monitor maybe performed for the links coupling between the communication apparatus,and it may be determined that an area failure has occurred based on thelink failure in at least one link coupled to another area.

Subsequently to Step S209, the network management server 9 identifiesthe recovery plane to be used when failures occur in the area “2” andthe area “6” (Step S210). Here, for example, the network managementserver 9 identifies the recovery plane “19” to be used when a failureoccurs in the area “2” and the area “6”. Subsequently to Step S210, thenetwork management server 9 notifies the transmission apparatus relatingto the recovery setting for the path of the identified recovery plane ID(19) (Steps S211-1 to S211-6). Specifically, for example, the networkmanagement server 9 notifies of the recovery plane ID by using themulticast network for the management control (not shown). It should benoted that in the first embodiment, the network management server 9notifies the transmission apparatus relating to the recovery of the pathof the recovery plane ID by using the multicast network, but mayindividually notify each of the transmission apparatus of the samerecovery plane ID.

After Step S211, the transmission apparatus executes path recoverysetting based on the recovery plane ID notified of by the networkmanagement server 9 and a path setting table for each recovery planereceived and held in advance, and executes the transmission of thereceived data (Steps S212-1 to S212-5). After Step S212, thecommunication system starts data transmission after the recovery (StepS213). This completes the recovery.

<Storage Content Example of Various Tables>

FIG. 5 is an explanatory diagram showing a storage content example of arecovery plane list table. A recovery plane list table 500 is a tablefor storing the recovery plane serving as a list of the paths forrecovering an active-system path for each area failure pattern.Specifically, the recovery plane list table 500 is a table for storing,in terms of the transmission path within the network, for eachoccurrence pattern (failure pattern) of a failure occurrence area inwhich a failure has occurred in the communication apparatus among aplurality of areas through which the transmission path passes:information (recovery plane ID and path) for identifying the recoverypaths corresponding to the occurrence pattern; and information (recoverysetting) for identifying the communication apparatus through which therecovery path passes, in association with each other.

The recovery plane list table 500 is a table created first in thecalculation of the recovery plane of Step S204 illustrated in FIG. 3. Asshown in FIG. 5, a situation in which a failure has occurred in none ofthe areas is managed as a currently operated system, and is set to havea recovery plane ID of “0”. It should be noted that the recovery planeID of “#” (# representing an integer equal to or greater than zero) isexpressed as “recovery plane “#””.

The transmission path P1 of the recovery plane “0” is a path passingfrom the terminal 101 through the communication apparatus 14, 11, 51,61, 62, 71, 31, and 34 to reach the terminal 103. Further, thetransmission path P2 of the recovery plane “0” is a path passing fromthe terminal 102 through the communication apparatus 23, 22, 62, 71, 72,82, 42, and 43 to reach the terminal 104. It should be noted thatunidirectional transmission path setting is described for thetransmission path P1 and the transmission path P2, but the transmissionpath setting for the reverse direction may be executed in the samemanner.

In regard to the area failure, for example, when failures have occurredin the area “2” and the area “6”, the network management server 9 refersto the recovery plane list table 500 to select the recovery plane “19”as the recovery plane. Further, in the recovery plane “19”, thetransmission path P1 is set as a path passing from the terminal 101through the communication apparatus 14, 11, 51, 52, 81, 32, 31, and 34to reach the terminal 103. In addition, in the recovery plane “19”, thetransmission path P2 is set as a path passing from the terminal 102through the communication apparatus 13, 12, 11, 51, 52, 81, 82, 42, and43 to reach the terminal 104.

Also for another area failure pattern in the area “1” and another areafailure pattern in the area “2”, the recovery plane “1” and the recoveryplane “2” are set, respectively, and the recovery planes correspondingto all the other failure patterns are set in the same manner. It shouldbe noted that in the first embodiment, in the calculation of thetransmission path in the recovery plane, the selection is performed soas to avoid passing through the failure area, but another method may beemployed, for example, the selection may be performed so as to achievethe shortest hop while avoiding passing through the failure area.

FIG. 6 to FIG. 9 are explanatory diagrams showing a storage contentexample of a path coupling setting table showing the coupling relationsbetween the transmission apparatus for each recovery plane. The pathcoupling setting table of FIG. 6 shows a path coupling setting for eachtransmission apparatus in a case where there is no failure area, inother words, in the currently operated system (recovery plane “0”). Thepath coupling setting table of FIG. 6 is obtained by rearranging thedata relating only to the recovery plane “0”, which is acquired from therecovery plane list table 500 of FIG. 5, in terms of the transmissionpath setting for each transmission apparatus.

In the recovery plane “0”, for example, the communication apparatus 11indicates a path coupling setting in which the data received from thecommunication apparatus 14 is transmitted to the communication apparatus51 while the data received from the communication apparatus 51 istransmitted to the communication apparatus 14 in terms of thetransmission path P1. The terminal 101 indicates a path coupling settingin which the data is transmitted to the communication apparatus 14 whilethe data is received from the communication apparatus 14. In the samemanner, also for the other transmission apparatus, the path couplingsettings are stored in the path coupling setting table of FIG. 6.

The path coupling setting table of FIG. 7 shows a recovery path couplingsetting for each transmission apparatus in the recovery plane “1” in acase where a failure occurs in the area “1”. The path coupling settingtable of FIG. 7 is obtained by rearranging the data relating only to therecovery plane “1”, which is acquired from the recovery plane list table500 of FIG. 5, in terms of the transmission path setting for eachtransmission apparatus.

In the recovery plane “1”, for example, the communication apparatus 24indicates a recovery path coupling setting in which the data receivedfrom the terminal 101 is transmitted to the communication apparatus 21while the data received from the communication apparatus 21 istransmitted to the terminal 101 in terms of the transmission path P1.The terminal 101 indicates a recovery path coupling setting in which thedata is transmitted to the communication apparatus 24 while the data isreceived from the communication apparatus 24. In the same manner, alsofor the other transmission apparatus, the recovery path couplingsettings are stored in the path coupling setting table of FIG. 7.

The path coupling setting table of FIG. 8 shows a recovery path couplingsetting for each transmission apparatus in the recovery plane “2” in acase where a failure occurs in the area “2”. The path coupling settingtable of FIG. 8 is obtained by rearranging the data relating only to therecovery plane “2”, which is acquired from the recovery plane list table500 of FIG. 5, in terms of the transmission path setting for eachtransmission apparatus.

In the recovery plane “2”, for example, the communication apparatus 13indicates a recovery path coupling setting in which the data receivedfrom the terminal 102 is transmitted to the communication apparatus 12while the data received from the communication apparatus 12 istransmitted to the terminal 102 in terms of the transmission path P2.The terminal 102 indicates a recovery path coupling setting in which thedata is transmitted to the communication apparatus 13 while the data isreceived from the communication apparatus 13. In the same manner, alsofor the other transmission apparatus, the path coupling settings arestored in the path coupling setting table of FIG. 8.

The path coupling setting table of FIG. 9 shows a recovery path couplingsetting for each transmission apparatus in the recovery plane “19” in acase where failures occur in the area “2” and the area “6”. The pathcoupling setting table of FIG. 9 is obtained by rearranging the datarelating only to the recovery plane “19”, which is acquired from therecovery plane list table 500 of FIG. 5, in terms of the transmissionpath setting for each transmission apparatus.

In the recovery plane “19, for example, the communication apparatus 51indicates a recovery path coupling setting in which the data receivedfrom the communication apparatus 11 is transmitted to the communicationapparatus 52 while the data received from the communication apparatus 52is transmitted to the communication apparatus 11 in terms of thetransmission path P1. Further, the communication apparatus 51 indicatesa recovery path coupling setting in which the data received from thecommunication apparatus 11 is transmitted to the communication apparatus52 while the data received from the communication apparatus 52 istransmitted to the communication apparatus 11 in terms of thetransmission path P2. In the same manner, also for the othertransmission apparatus, the recovery path coupling settings are storedin the path coupling setting table of FIG. 9.

FIG. 10 to FIG. 16 are explanatory diagrams showing a storage contentexample of a recovery path setting list table for each recovery planecorresponding to each transmission apparatus. The recovery path settinglist table shows recovery information including: information foridentifying recovery paths passing through an own apparatus; andinformation for designating coupling counterparts to which the ownapparatus is to be coupled in the recovery path passing through the ownapparatus.

The recovery path setting list table of FIG. 10 shows a recovery pathsetting list for each recovery plane corresponding to the communicationapparatus 31. For example, the recovery plane “19” indicates a recoverypath setting in which the communication apparatus 31 transmits the datareceived from the communication apparatus 32 to the communicationapparatus 34 while transmitting the data received from the communicationapparatus 34 to the communication apparatus 32 in terms of thetransmission path P1. In the same manner, also for the other recoveryplanes, the recovery path settings are stored in the recovery pathsetting list table of FIG. 10.

The recovery path setting list table of FIG. 11 shows a recovery pathsetting list for each recovery plane corresponding to the communicationapparatus 42. For example, the recovery plane “19” indicates a recoverypath setting in which the communication apparatus 42 transmits the datareceived from the communication apparatus 82 to the communicationapparatus 43 while transmitting the data received from the communicationapparatus 43 to the communication apparatus 82 in terms of thetransmission path P2. In the same manner, also for the other recoveryplanes, the recovery path settings are stored in the recovery pathsetting list table of FIG. 11.

The recovery path setting list table of FIG. 12 shows a recovery pathsetting list for each recovery plane corresponding to the communicationapparatus 51. For example, the recovery plane “19” indicates a recoverypath setting in which the communication apparatus 51 transmits the datareceived from the communication apparatus 11 to the communicationapparatus 52 while transmitting the data received from the communicationapparatus 52 to the communication apparatus 11 in terms of thetransmission path P1. Further, the communication apparatus 51 indicatesa recovery path coupling setting in which the data received from thecommunication apparatus 11 is transmitted to the communication apparatus52 while the data received from the communication apparatus 52 istransmitted to the communication apparatus 11 in terms of thetransmission path P2. In the same manner, also for the other recoveryplanes, the recovery path settings are stored in the recovery pathsetting list table of FIG. 12.

The recovery path setting list table of FIG. 13 shows a recovery pathsetting list for each recovery plane corresponding to the terminal 101.For example, the recovery plane “19” indicates a recovery path settingin which the terminal 101 transmits the data to the communicationapparatus 14 while receiving the data from the communication apparatus14 in terms of the transmission path P1. In the same manner, also forthe other recovery planes, the recovery path settings are stored in therecovery path setting list table of FIG. 13.

The recovery path setting list table of FIG. 14 shows a recovery pathsetting list for each recovery plane corresponding to the terminal 102.For example, the recovery plane “19” indicates a recovery path settingin which the terminal 102 transmits the data to the communicationapparatus 13 while receiving the data from the communication apparatus13 in terms of the transmission path P2. In the same manner, also forthe other recovery planes, the recovery path settings are stored in therecovery path setting list table of FIG. 14.

The recovery path setting list table of FIG. 15 shows a recovery pathsetting list for each recovery plane corresponding to the terminal 103.For example, the recovery plane “19” indicates a recovery path settingin which the terminal 103 receives the data from the communicationapparatus 34 while transmitting the data to the communication apparatus34 in terms of the transmission path P1. In the same manner, also forthe other recovery planes, the recovery path settings are stored in therecovery path setting list table of FIG. 15.

The recovery path setting list table of FIG. 16 shows a recovery pathsetting list for each recovery plane corresponding to the terminal 104.For example, the recovery plane “19” indicates a recovery path settingin which the terminal 104 receives the data from the communicationapparatus 43 while transmitting the data to the communication apparatus43 in terms of the transmission path P2. In the same manner, also forthe other recovery planes, the recovery path settings are stored in therecovery path setting list table of FIG. 16.

<Hardware Configuration Example of Network Management Server 9>

FIG. 17 is a block diagram illustrating a hardware configuration exampleof the network management server 9 according to the first embodiment.The network management server 9 includes a CPU 91, a memory 92, astorage 93, and a network interface 94, and the respective componentsare coupled to one another through a bus 90. The CPU 91 loads variousprograms stored in the storage 93 onto the memory 92 to execute theprograms. The CPU 91 executes the programs, to thereby be able toimplement functions provided to the network management server 9. Thememory 92 stores the programs to be executed by the CPU 91 and datanecessary to execute the programs. The programs and data stored in thememory 92 are described later with reference to FIG. 18. The networkinterface 94 is an interface for coupling to an external network. FIG.17 illustrates one interface coupled to the external network, but aplurality of interfaces may be mounted.

FIG. 18 is a block diagram illustrating a functional configurationexample of the network management server 9 according to the firstembodiment. When the CPU 91 executes the programs stored in the memory,the network management server 9 executes active-system path calculationprocessing 300, area-failure-basis recovery plane calculation processing301, recovery-plane-basis recovery path calculation processing 302,apparatus-basis recovery plane calculation processing 303, area monitorprocessing 304, and path setting processing 305.

In the active-system path calculation processing 300, a path settinginput is received from the network administrator or the like, and theset path for the respective communication apparatus to be operated asthe transmission path P1 for the active system is calculated inaccordance with the input path setting, for example, an input of a pathsetting of 1 Gbps between the terminal 101 and the terminal 103. Thecalculated set path is held in the memory 92 as an active-system pathsetting database 310. In the first embodiment, the transmission path P1passing from the terminal 101 through the communication apparatus 14,11, 51, 61, 62, 71, 31, and 34 to reach the terminal 103 is set by theactive-system path calculation processing 300. The setting is performedfor the respective communication apparatus. It should be noted thatbetween the terminal 101 and the terminal 103, the path setting may beperformed bidirectionally with the same transmission quality, or may beperformed unidirectionally with different transmission quality. Further,in the same manner, the active-system path calculation processing 300sets the transmission path P2 between the terminal 102 and the terminal104 as the transmission path P2.

In the area-failure-basis recovery plane calculation processing 301,setting for managing a plurality of communication apparatus collectivelyas areas is performed in the entire communication system in accordancewith the input from the network administrator or the like. Further, inthe area-failure-basis recovery plane calculation processing 301, therecovery plane formed of the path list for recovering the active-systempath for each area failure pattern shown in FIG. 5 is calculated, and isheld in the memory 92 as an area-failure-basis recovery plane database311.

In the recovery-plane-basis recovery path calculation processing 302,the recovery path setting for each recovery plane shown in, for example,FIG. 6 to FIG. 9 is calculated from the area-failure-basis recoveryplane database 311 calculated in the area-failure-basis recovery planecalculation processing 301, and is held in the memory 92 as arecovery-plane-basis path setting database 312.

In the apparatus-basis recovery plane calculation processing 303, therecovery path setting list table for each recovery plane correspondingto each transmission apparatus shown in, for example, FIG. 10 to FIG. 16is calculated from the recovery-plane-basis path setting database 312calculated in the recovery-plane-basis recovery path calculationprocessing 302, and is held in the memory 92 as an apparatus-basisrecovery plane database 313.

In the area monitor processing 304, an operation situation of eachcommunication apparatus is monitored, it is determined along with thedetection of the occurrence of the failure whether or not a failure hasoccurred in units of areas, and failure information obtained in thecommunication apparatus and the area is held in the memory 92 as afailure area database 314.

In the path setting processing 305, the communication apparatus isnotified of the path setting determined in the active-system pathcalculation processing and the recovery plane ID determined in the areamonitor processing 304.

It should be noted that the processing flows of the area-failure-basisrecovery plane calculation processing 301, the recovery-plane-basisrecovery path calculation processing 302, and the apparatus-basisrecovery plane calculation processing 303 are described with referenceto flowcharts of FIG. 19 and of FIG. 20. Further, the processing flowsof the area monitor processing 304 and the path setting processing 305are described with reference to a flowchart of FIG. 21.

<Processing Flow Example of Network Management Server 9>

FIG. 19 is a flowchart illustrating a processing procedure example ofthe calculation of a failure recovery plane and recovery planeinformation notification to the respective communication apparatus thatare executed by the network management server 9 according to the firstembodiment. This flowchart is a preprocessing for area-basis failuremonitor control. The network management server 9 (CPU 91) loads theprogram stored in the storage 93 onto the memory 92 to execute theprogram, and starts calculation setting for an area failure recoveryplane (Step S350).

In accordance with the input from the network administrator, the networkmanagement server 9 performs area partitioning collectively for eachplurality of communication apparatus forming the communication system tobe managed (Step S351). It should be noted that, for example, thenetwork management server 9 performs the area partitioning by usingpositional information held by the communication apparatus. In the firstembodiment, the communication apparatus are partitioned into areas inaccordance with the input from the network administrator, butpartitioning of areas may be stored in a storage or the like as adatabase in advance.

The network management server 9 enumerates the area failure patternsafter Step S351, and assigns the recovery plane ID to each thereof (StepS352). In the first embodiment, the management is carried out bypartitioning into the eight areas, and hence the recovery plane IDs areassigned so as to correspond to two hundred fifty-six patterns in total.

The network management server 9 calculates, after Step S352, the pathsetting for the recovery plane for each area failure pattern shown inFIG. 5 (Step S353). The network management server 9 calculates, afterStep S353, the path setting for each recovery plane shown in FIG. 6 toFIG. 9 (Step S354). The network management server 9 calculates, afterStep S354, the path setting for each communication apparatus and foreach recovery plane shown in FIG. 10 to FIG. 16 (Step S355).

The network management server 9 notifies the respective communicationapparatus of a recovery plane database for each communication apparatuscalculated in Step S355 (Step S356). The network management server 9starts, after Step S356, a process for the area-basis failure monitorcontrol (Step S380).

FIG. 20 is a flowchart illustrating a detailed processing procedureexample of recovery path calculation processing (Step S353) executed bythe network management server 9 according to the first embodiment. Thenetwork management server 9 starts calculation of a recovery plane pathfor each area failure pattern (Step S360). The network management server9 selects, after Step S360, one recovery plane for which a recovery pathhas not been set (Step S361).

The network management server 9 selects one active-system path for whicha recovery path has not been set for the recovery plane selected in StepS361 (Step S362). As a selection method, the selection may be performedin descending order of priority. Further, the selection may be performedin descending order of priority of a bandwidth necessary for the path,or another method using, for example, a priority based on a servicecontract may be used.

The network management server 9 executes processing for calculating therecovery path for the active-system path selected in Step S362 (StepS363). In the calculation of the recovery path, processing forcalculating the transmission path for the recovery is executed so as toavoid passing through the area in which a failure occurrence is assumedand so as to minimize the hop count within a range of the paths that cansecure the necessary bandwidth.

The network management server 9 determines whether or not the recoverypath has been successfully calculated in the processing of Step S363(Step S364). When it is determined in Step S364 that the recovery pathhas been successfully calculated (Step S364: Yes), the calculated pathis set as the recovery path (Step S365). Subsequently to Step S365, thenetwork management server 9 determines whether or not the recovery pathsfor all the paths set for the active system have been searched (StepS366).

When it is determined in Step S366 that recovery path searches have notbeen completed for all the paths for the active system (Step S366: No),the procedure returns to Step S362 to continue the processing. When itis determined in Step S366 that the recovery path searches have beencompleted for all the paths for the active system (Step S366: Yes), itis determined whether or not the recovery path searches have beencompleted for all the recovery planes (Step S367).

When it is determined in Step S367 that the recovery path searches havenot been completed for all the recovery planes (Step S367: No), theprocedure returns to Step S361 to continue the processing. When it isdetermined in Step S367 that the recovery path searches have beencompleted for all the recovery planes (Step S367: Yes), the recoverypath calculation processing for each recovery plane is finished (StepS368), and the processing of Step S354 illustrated in FIG. 19 isstarted.

When it is determined in Step S364 that the recovery path has not beensuccessfully calculated (Step S364: No), it is determined whether or notthe recovery path can be calculated through the change of analready-existing recovery path (Step S369). In the calculation of therecovery path (Step S363), for example, the transmission path for therecovery is calculated so as to avoid passing through the area in whicha failure occurrence is assumed, so as to be able to secure thenecessary bandwidth, and so as to minimize the hop count.

In contrast, in Step S369, the network management server 9 attempts tochange the already-existing recovery path calculated in the calculationof the recovery path (Step S363) so as to avoid passing through the areain which a failure occurrence is assumed and so as to secure thenecessary bandwidth, to thereby determine whether or not the recoverypath after the change can be calculated. It is preferred that the hopcount be minimized, but the hop count that is not minimized may beallowed. In the case where the already-existing recovery path has beenchanged, the calculation of the recovery path (Step S369) is executedfor the currently-selected active-system path. When it is determined inStep S369 that the recovery path cannot be calculated (Step S369: No),the processing of Step S362 is executed.

When it is determined in Step S369 that the recovery path can becalculated (Step S369: Yes), the recovery path after the change for thecurrently-processed active-system path is calculated by changing thealready-existing recovery path, and sets the calculated path as therecovery path (Step S370), to continue the processing of Step S366.

FIG. 21 is a flowchart illustrating a detailed processing procedureexample of the monitor of the failure and recovery plane notificationthat are executed by the network management server 9 according to thefirst embodiment. After notifying the respective communication apparatusof recovery path setting information for each recovery plane, thenetwork management server 9 starts failure monitor control processing inunits of areas and units of operation states of the respectivecommunication apparatus (Step S380).

After starting the processing of Step S380, the network managementserver 9 detects whether or not a failure has occurred in thecommunication apparatus (Step S381). In the first embodiment, in thefailure monitor of the communication apparatus, it is determined that,when there is no response from a communication apparatus beingmonitored, a failure has occurred in the communication apparatus.

When it is determined in Step S381 that a failure has not been detectedin the communication apparatus, the failure detection processing for thecommunication apparatus is continued. When it is determined in Step S381that a failure has been detected in the communication apparatus, thenetwork management server 9 holds detected communication apparatusfailure information (Step S382).

Subsequently to Step S382, the network management server 9 startsmeasuring time from the first failure occurrence (Step S383).Subsequently to Step S383, the network management server 9 determineswhether or not a fixed time period, for example, 10 seconds has elapsed(Step S384). In the first embodiment, 10 seconds is set as the fixedtime period, but another value, for example, a value such as 1 second or1 minute may be set. By thus performing the determination within a fixedtime period, the recovery can be performed collectively even whenfailures have occurred in a plurality of areas within the fixed timeperiod.

When it is determined in Step S384 that the fixed time period has notelapsed, the network management server 9 continues to detect whether ornot a failure has occurred in another communication apparatus, and whena failure has been detected, registers the failure information (StepS390). When it is determined in Step S384 that the fixed time period haselapsed, the network management server 9 determines whether or not thereis a failure detection record of the communication apparatus (StepS385).

When it is determined in Step S385 that there is no failure detectionrecord of the communication apparatus, the network management server 9returns to Step S381 to continue the processing. When it is determinedin Step S385 that there is a failure detection record of thecommunication apparatus, the network management server 9 resets therecord of the elapsed time (Step S386).

Subsequently to Step S386, the network management server 9 determineswhether or not there is an area failure based on the record of thedetected communication apparatus failure (Step S387). The networkmanagement server 9 determines the recovery plane based on thedetermined area failure information (Step S388). The network managementserver 9 notifies the respective transmission apparatus of the ID of thedetermined recovery plane (Step S389), and returns to Step S384 tocontinue the processing.

<Hardware Configuration Example of Communication Apparatus>

FIG. 22 is a block diagram illustrating a hardware configuration exampleof the communication apparatus (11, 12, 13, 14, 21, 22, 23, 24, 31, 32,33, 34, 41, 42, 43, 44, 51, 52, 61, 62, 71, 72, 81, and 82) according tothe first embodiment. The communication apparatus includes networkinterfaces 110-1 to 110-n, a switch 111, a table management module 112,a data transfer table 113, and a used table control module 116. Further,the data transfer table 113 includes an active-system table 114 showingactive-system path settings and a recovery plane table 115 showing pathsettings within the recovery plane.

The communication apparatus receives data for the path setting and therecovery plane ID through the network interfaces 110. When receivingdata for transfer, the switch 111 switches the data to a networkinterface of an output destination based on an active-system table fordata transfer. On the other hand, when the received data is the data forthe path setting and the recovery plane ID, the communication apparatusswitches the received data to the table management module 112. When thereceived data is the path setting, the table management module 112updates the active-system table 114 or the recovery plane table 115. Forexample, the recovery path setting list table for each apparatus (FIG.10 to FIG. 16) is stored in the recovery plane table 115.

On the other hand, when the received data is the recovery plane ID fornotifying of the recovery plane, the table management module 112notifies the used table control module 116 of the received recoveryplane ID. The used table control module 116 updates the active-systemtable used by the switch 111 for transfer of received data to a transfertable indicated by the recovery plane ID based on the recovery plane IDreceived from the table management module 112.

In this manner, according to the first embodiment, the recovery path atthe occurrence of the failure is calculated before the failureoccurrence, and hence an optimal recovery path can be calculated withmuch time to spare. Further, the calculated recovery path is deliveredto each communication node before the failure occurrence, and hence therecovery path can be notified of without any influence of the failure.In addition, when a failure occurs, the recovery path setting of whicheach node has been notified is used, and hence the path in which thefailure has occurred can be recovered quickly. Further, a recoverynotification for instructing a plurality of apparatus to recover thepath in which a failure has occurred can be transmitted from the networkmanagement server at one time by the same instruction, which allows aquick path recovery notification.

Second Embodiment

A communication system according to a second embodiment of thisinvention is different from the communication system according to thefirst embodiment in that area management servers 1 to 8 are provided tothe respective areas. It should be noted that the other components arethe same. The same components as those of the first embodiment aredenoted by the same reference symbols, and descriptions thereof areomitted.

<Network Configuration Example>

FIG. 23 is an explanatory diagram illustrating a system configurationexample of the communication system according to the second embodiment.Before starting the operation of the communication system, the networkmanagement server 9 notifies the area management servers 1 to 8 and theterminals of the path settings for the recovery planes corresponding toall the area failure patterns along with the recovery plane IDs. Thearea management servers 1 to 8 and the terminals hold the receivedrecovery plane IDs and the received recovery path settings correspondingto the respective communication apparatus within the areas.

FIG. 24 is an explanatory diagram illustrating a system configurationexample of the communication system after the failure recovery accordingto the second embodiment. In the first embodiment, the networkmanagement server 9 directly monitors and determines the failure inunits of communication apparatus and in units of areas, but in thesecond embodiment, the area management servers 1 to 8 monitor anddetermine the failure in units of communication apparatus and in unitsof areas.

After determining the failure in units of areas, the area managementservers 1 to 8 notify the network management server 9 of a result of thedetermination. The network management server 9 determines the recoveryplane based on the received area failure information, and notifies thearea management servers and the terminals of the recovery plane ID.Based on the received recovery plane ID, the area management servers 1to 8 notify the respective communication apparatus within the area ofthe recovery path setting corresponding to the respective communicationapparatus. Each of the communication apparatus executes the transmissionof the received data in accordance with the setting of the recovery pathnotified of. Further, the terminal carries out the switching of thecommunication apparatus for a data transmission/reception destinationbased on the recovery plane ID received in the same manner.

<Failure Recovery Sequence Example>

FIG. 25 is a sequence diagram (first half) illustrating a flow of thefailure recovery according to the second embodiment. It should be notedthat the sequence from the input of a path request (Step S201) to thecalculation of the recovery plane for each communication apparatus (StepS206) is the same as the sequence of the first embodiment illustrated inFIG. 3, and hence a description thereof is omitted.

After that, the network management server 9 notifies the area managementservers 1 to 8 and the terminals of the path settings for the respectivecalculated recovery planes for each communication apparatus along withthe recovery plane IDs (Steps S250-1 to S250-9). The area managementservers 1 to 8 within the respective areas monitor whether or not afailure has occurred in the respective communication apparatus withinthe own area (Steps 251-1 to 251-8). The network management server 9monitors the area failure information transmitted from the respectivearea management servers (Steps S252-1 to S252-8).

FIG. 26 is a sequence diagram (second half) illustrating a flow of thefailure recovery according to the second embodiment. Subsequently toStep S252, the network management server 9 determines the occurrence ofa failure in units of areas (Step S209), and identifies the recoveryplane (Step S210). The network management server 9 notifies the areamanagement server necessary to recover the path of the identifiedrecovery plane ID (Steps S253-1 to S253-6). The area management serverthat has received the notification notifies the respective communicationapparatus within the own area of the recovery path settingscorresponding to the communication apparatus based on the recovery planeID (Steps S254-1 to S254-6). The network management server 9 notifiesthe terminal apparatus necessary to recover the path of the identifiedrecovery plane ID (Step 255). Subsequently to Step S255, the respectivetransmission apparatus perform transmission/reception of data inaccordance with the recovery path settings.

FIG. 27 is a flowchart illustrating a processing procedure example ofthe calculation of the failure recovery plane and the recovery planeinformation notification to the respective area management servers thatare executed by the network management server 9 according to the secondembodiment. In the first embodiment illustrated in FIG. 19, the networkmanagement server 9 notifies the respective communication apparatus ofinformation on a recovery plane path for each communication apparatus,but the second embodiment is different from the first embodiment in thatthe network management server 9 notifies the area management servers ofthe information. The same processing as that of FIG. 19 is denoted bythe same step number, and a description thereof is omitted. The secondembodiment is different from the first embodiment in that, as indicatedin Step S357, the network management server 9 notifies the areamanagement servers 1 to 8 of the information on the recovery plane pathsfor each communication apparatus along with the recovery plane IDs.

FIG. 28 is a flowchart illustrating a processing procedure example ofthe monitor of the failure and recovery plane notification that areexecuted by the network management server 9 according to the secondembodiment. In the first embodiment illustrated in FIG. 21, the networkmanagement server 9 directly monitors the failure in the communicationapparatus, but in the second embodiment, the network management server 9executes the monitor of the respective communication apparatus and thearea failure through the intermediation of the area management server.The same processing as that of FIG. 21 is denoted by the same stepnumber.

The network management server 9 notifies the respective area managementservers of the recovery path setting information for each recoveryplane, and then starts failure monitor control processing in units ofareas (Step S380). After starting the processing of Step S380, thenetwork management server 9 detects whether or not a failure hasoccurred in a monitored area (Step S395). In the second embodiment, thenetwork management server 9 detects the area failure based on a failurenotification in units of areas received from the area management server.Further, when there is no response from the area management server, thenetwork management server 9 determines that a failure has occurred inthe area corresponding thereto.

When it is determined in Step S395 that a failure has not been detectedin the monitored area (Step S395: No), the network management server 9continues the failure detection processing for the monitored area. Whenit is determined in Step S395 that a failure has been detected in themonitored area (Step S395: Yes), the network management server 9 holdsdetected area failure information (Step S396).

Subsequently to Step S396, the network management server 9 startsmeasuring time from the first area failure occurrence (Step S383).Subsequently to Step S383, the network management server 9 determineswhether or not a fixed time period, for example, 10 seconds has elapsed(Step S384). In the second embodiment, 10 seconds is set as the fixedtime period, but another value, for example, a value such as 1 second or1 minute may be set.

When it is determined in Step S384 that the fixed time period has notelapsed (Step S384: No), the network management server 9 continues todetect whether or not a failure has occurred in another area, and when afailure has been detected, registers the failure information (StepS397), to return to Step S384.

When it is determined in Step S384 that the fixed time period haselapsed (Step S384: Yes), the network management server 9 determineswhether or not there is a record of area failure detection (Step S398).When it is determined in Step S398 that there is no record of the areafailure detection (Step S398: No), the network management server 9returns to Step S395 to continue the processing.

When it is determined in Step S398 that there is a record of the areafailure detection (Step S398: Yes), the network management server 9resets the record of the elapsed time (Step S386). Subsequently to StepS386, the network management server 9 determines whether or not there isan area failure for all the areas based on the record of the detectedarea failure (Step S399). The network management server 9 determines therecovery plane based on the determined area failure information (StepS388). The network management server 9 notifies the area managementservers and the terminals of the determined recovery plane ID (StepS400), and returns to Step S384 to continue the processing.

FIG. 29 is a flowchart illustrating a processing procedure example ofprocessing in which the area management servers 1 to 8 notify therespective communication apparatus of the recovery path according to thesecond embodiment. When an area management server processing program isstarted (Step S410), the area management servers 1 to 8 determinewhether or not the recovery path setting information for eachcommunication apparatus within the own area and the recovery plane IDshave been received (Step S411).

When it is determined in Step S411 that the recovery path settinginformation for each communication apparatus and the recovery plane IDshave not been received (Step S411: No), the area management servers 1 to8 continue the processing of Step S411. When it is determined in StepS411 that the recovery path setting information for each communicationapparatus and the recovery plane IDs have been received (Step S411:Yes), the received data is updated and held (Step S412).

Subsequently to Step S412, the area management servers 1 to 8 determinewhether or not the recovery plane ID for area failure recovery has beenreceived (Step S413). When it is determined in Step S413 that therecovery plane ID has not been received (Step S413: No), the processingof Step S413 is continued. When it is determined in Step S413 that therecovery plane ID has been received (Step S413: Yes), the areamanagement servers 1 to 8 identify the recovery path settingscorresponding to the respective communication apparatus within the ownarea based on the recovery plane ID, and notify the respectivecommunication apparatus thereof (Step S414). Subsequently to Step S414,the processing of Step S413 is continued.

FIG. 30 is a flowchart illustrating a processing procedure example of afailure monitor processing operation executed by the area managementserver according to the second embodiment. The area management servers 1to 8 activate the area management server processing program to startarea failure monitor control processing (Step S420). Subsequently toStep S420, the area management servers 1 to 8 detect whether or not afailure has occurred in the communication apparatus within the own area(Step S421). In the second embodiment, in the failure monitor of thecommunication apparatus, it is determined that, when there is noresponse from a communication apparatus being monitored, a failure hasoccurred in the communication apparatus.

When it is determined in Step S421 that a failure has not occurred inthe communication apparatus (Step S421: No), the area management servers1 to 8 continue the failure detection processing for the communicationapparatus. When it is determined in Step S421 that a failure has beendetected in the communication apparatus (Step S421: Yes), the areamanagement servers 1 to 8 hold the detected communication apparatusfailure information (Step S422).

Subsequently to Step S422, the area management servers 1 to 8 startmeasuring time from the first failure occurrence (Step S423).Subsequently to Step S423, the area management servers 1 to 8 determinewhether or not a fixed time period, for example, 10 seconds has elapsed(Step S424). In the second embodiment, 10 seconds is set as the fixedtime period, but another value, for example, a value such as 1 second or1 minute may be set.

When it is determined in Step S424 that the fixed time period has notelapsed (Step S424: No), the area management servers 1 to 8 continue todetect whether or not a failure has occurred in another communicationapparatus, and when a failure has been detected, register the failureinformation (Step S430), to return to Step S424. When it is determinedin Step S424 that the fixed time period has elapsed (Step S424: Yes),the area management servers 1 to 8 determine whether or not there is afailure detection record of the communication apparatus (Step S425).

When it is determined in Step S425 that there is no failure detectionrecord of the communication apparatus (Step S425: No), the areamanagement servers 1 to 8 return to Step S421 to continue theprocessing. When it is determined in Step S425 that there is a failuredetection record of the communication apparatus (Step S425: Yes), thearea management servers 1 to 8 reset the record of the elapsed time(Step S426).

Subsequently to Step S426, the area management servers 1 to 8 determinewhether or not there is an area failure based on the record of thedetected communication apparatus failure (Step S427). The areamanagement servers 1 to 8 notify the network management server 9 of thedetermined area failure information (Step S428), to finish area failuremonitor control processing (Step S429). When the network managementserver 9 is notified of the area failure information (Step S428), thenetwork management server 9 determines that an area failure has occurredas indicated in Step S209 of FIG. 26.

In this manner, according to the second embodiment, in the same manneras in the first embodiment, the recovery path at the occurrence of thefailure is calculated before the failure occurrence, and hence anoptimal recovery path can be calculated with much time to spare.Further, in the same manner as in the first embodiment, the calculatedrecovery path is delivered to each communication node before the failureoccurrence, and hence the recovery path can be notified of without anyinfluence of the failure. Further, by providing the respective areaswith the area management servers 1 to 8 to notify the area managementservers 1 to 8, instead of the communication apparatus, of the recoverypath, it is possible to achieve load balancing of the network managementserver 9.

Further, in the same manner as in the first embodiment, when a failureoccurs, the recovery path setting of which each node has been notifiedis used, and hence the path in which the failure has occurred can berecovered quickly. Further, a recovery notification for instructing thearea management servers 1 to 8 to recover the path in which a failurehas occurred can be transmitted from the network management server atone time by the same instruction. In other words, it is not necessary tonotify the individual communication apparatus, and hence it is possibleto achieve the load balancing of the network management server 9.

Third Embodiment

A third embodiment of this invention relates to an example in which afunction that enables independent failure recovery within the area isadded to the second embodiment.

FIG. 31 is a flowchart illustrating a processing procedure example forthe path recovery within the area according to the third embodiment. Inthe third embodiment, the area management servers 1 to 8 activate thearea management server processing program to start the area failuremonitor control processing (Step S450). Subsequently to Step S450, thearea management servers 1 to 8 determine whether or not a notificationof a link failure has been received from the communication apparatuswithin the area (Step S451). When it is determined in Step S451 that thelink failure has not been detected (Step S451: No), the area managementservers 1 to 8 continue the processing of Step S451.

When it is determined in Step S451 that the link failure has beendetected (Step S451: Yes), the area management servers 1 to 8 determinewhether or not the independent recovery is possible within the area(Step S452). When it is determined in Step S452 that the recovery withinthe area is possible (Step S452: Yes), the area management servers 1 to8 execute the recovery within the area (Step S453).

In the determination of Step S452, the area management servers 1 to 8may determine that the independent recovery is impossible within thearea only by, for example, detecting a link failure. Further, even whenthere is a link failure, in a case where an alternative path existswithin the area, the area management servers 1 to 8 may determine thatthe recovery is possible.

Subsequently to Step S453, the area management servers 1 to 8 notify thenetwork management server 9 of alternative path information within thearea (Step S454). The alternative path information includes theinformation on the path before bypassing and the path after bypassingwithin the area. The network management server 9 corrects theinformation on the active-system path based on the alternative pathinformation. For example, when a communication apparatus that forms thepath before bypassing exists in the transmission paths P1 and P2 of therecovery plane ID of “0”, the network management server 9 corrects acontent of the recovery setting to the path after bypassing. In the samemanner, the network management server 9 corrects the recovery plane listtable 500 of FIG. 5 and entries of the recovery plane ID of “0” shown inFIG. 10 to FIG. 16 based on the alternative path information.

Subsequently to Step S454, the area management servers 1 to 8 return toStep S451 to continue the processing. When it is determined in Step S452that the recovery within the area is impossible (Step S452: No), thearea management servers 1 to 8 notify the network management server 9 ofthe area failure (Step S455), to finish the area failure monitor controlprocessing (Step S456). When the network management server 9 is notifiedof the area failure information (Step S456), the network managementserver 9 determines that an area failure has occurred as indicated inStep S209 of FIG. 26.

In this manner, according to the third embodiment, the failureoccurrence can be determined within the area, and it is possible toachieve reduction in load on the network management server 9. It shouldbe noted that the third embodiment can also be applied to the firstembodiment. In this case, the network management server 9 executes theprocessing of FIG. 31.

Fourth Embodiment

The description of the second embodiment is directed to the example inwhich the network management server 9 notifies the area managementservers 1 to 8 of the recovery plane ID, and the area management servers1 to 8 identify the recovery path setting corresponding to therespective communication apparatus within the own area based on therecovery plane ID, and notify the respective communication apparatus ofthe recovery path setting. In a fourth embodiment of this invention, thenetwork management server 9 notifies the respective communicationapparatus of the recovery plane ID, and the respective communicationapparatus execute processing for receiving the recovery path settingsfor the respective communication apparatus from the area managementservers 1 to 8.

In this manner, according to the fourth embodiment, the communicationapparatus receives the recovery plane ID, and hence can transmit arequest for acquiring the recovery path setting to the corresponding oneof the area management servers 1 to 8. Therefore, when the recovery pathsetting cannot be received even though the request for acquiring therecovery path setting is transmitted, the communication apparatus candetermine that a failure has occurred in the corresponding one of thearea management servers 1 to 8. In this case, the communicationapparatus notifies the network management server 9 of the failureinformation on the area management server. Based on this notification,the network management server 9 determines that a failure has occurredin the area, and the recovery can be performed as described above.

Fifth Embodiment

In the second to fourth embodiments, the network management server 9selects the recovery plane based on the failure occurrence in units ofareas. In a fifth embodiment of this invention, the area managementservers 1 to 8 exchange the failure occurrence information in units ofareas with one another or confirm operations of one another, and thearea management server itself determines the failure occurrences inunits of areas within all the areas, and selects the recovery plane.

In this manner, according to the fifth embodiment, the same effect canbe produced as the effect described in the second to fourth embodiments.Further, the management for each area can be realized in an autonomousdistributed manner.

It should be noted that the above-mentioned embodiments are described bytaking the example in which the recovery is performed in units of areas,but the recovery may be performed in units of communication apparatus.

It should be noted that this invention is not limited to theabove-mentioned embodiments, and encompasses various modificationexamples and the equivalent configurations within the scope of theappended claims without departing from the gist of this invention. Forexample, the above-mentioned embodiments are described in detail for abetter understanding of this invention, and this invention is notnecessarily limited to what includes all the configurations that havebeen described. Further, a part of the configurations according to agiven embodiment may be replaced by the configurations according toanother embodiment. Further, the configurations according to anotherembodiment may be added to the configurations according to a givenembodiment. Further, a part of the configurations according to eachembodiment may be added to, deleted from, or replaced by anotherconfiguration.

Further, a part or entirety of the respective configurations, functions,processing modules, processing means, and the like that have beendescribed may be implemented by hardware, for example, may be designedas an integrated circuit, or may be implemented by software by aprocessor interpreting and executing programs for implementing therespective functions.

The information on the programs, tables, files, and the like forimplementing the respective functions can be stored in a storage devicesuch as a memory, a hard disk drive, or a solid state drive (SSD) or arecording medium such as an IC card, an SD card, or a DVD.

Further, control lines and information lines that are assumed to benecessary for the sake of description are described, but not all thecontrol lines and information lines that are necessary in terms ofimplementation are described. It may be considered that almost all thecomponents are connected to one another in actuality.

What is claimed is:
 1. A network management server to be coupled tocommunication apparatus within respective areas of an area group forminga network, the network management server comprising: a processor forexecuting a program; a memory for storing the program to be executed bythe processor; an interface for controlling communications to/from eachof the communication apparatus; and a storage for storing data, wherein:the storage stores, in terms of a transmission path within the network,for each occurrence pattern of a failure occurrence area in which afailure has occurred in the communication apparatus among a plurality ofareas through which the transmission path passes: information foridentifying a recovery plane serving as a set of recovery pathscorresponding to the each occurrence pattern; and information foridentifying the communication apparatus through which each of therecovery paths passes, in association with each other; the communicationapparatus each store recovery information comprising: information foridentifying the recovery plane serving as the set of recovery pathspassing through an own apparatus; and information for designatingcoupling counterparts to which the own apparatus is to be coupled ineach of the recovery paths passing through the own apparatus; and thenetwork management server executes: an identification procedure ofidentifying, when a failure occurs in any one of the plurality of areas,whether or not the failure corresponds to any one of failure occurrencepatterns; an acquisition procedure of acquiring the information foridentifying the recovery plane corresponding to the one of failureoccurrence patterns identified in the identification procedure from thestorage; and a notification procedure of notifying the communicationapparatus through which each of the recovery paths included in therecovery plane passes of the information for identifying the recoveryplane acquired in the acquisition procedure.
 2. The network managementserver according to claim 1, wherein the notification procedurecomprises notifying of the information for identifying the same recoveryplane.
 3. The network management server according to claim 1, wherein:the network management server executes a transmission procedure oftransmitting, to each of the communication apparatus, the recoveryinformation on the recovery path passing through the each of thecommunication apparatus; and the identification procedure comprisesidentifying whether or not the failure corresponds to any one of thefailure occurrence patterns after execution of the transmissionprocedure.
 4. The network management server according to claim 3,wherein: the network management server executes: a calculation procedureof calculating the recovery paths corresponding to the occurrencepattern; and a generation procedure of generating the information fordesignating the coupling counterparts to which the communicationapparatus through which each of the recovery paths calculated in thecalculation procedure passes is to be coupled; and the transmissionprocedure comprises transmitting the recovery information comprising theinformation for designating the coupling counterparts generated in thegeneration procedure.
 5. The network management server according toclaim 1, wherein: the network management server executes a determinationprocedure of determining, based on the failure that has occurred in thecommunication apparatus within any one of the plurality of areas,whether or not the any one of the plurality of areas corresponds to thefailure occurrence area in which the communications are disabled; andthe identification procedure comprises identifying whether or not thefailure corresponds to any one of the failure occurrence patterns basedon a determination result determined in the determination procedure. 6.The network management server according to claim 5, wherein thedetermination procedure comprises determining the failure occurrencearea within a predetermined period.
 7. The network management serveraccording to claim 5, wherein the determination procedure comprisesdetermining the any one of the plurality of areas as the failureoccurrence area when a link to another area, which is provided to thecommunication apparatus within the any one of the plurality of areas,becomes disabled.
 8. The network management server according to claim 5,wherein the determination procedure comprises determining the any one ofthe plurality of areas as the failure occurrence area based on a numberof communication apparatus in each of which a failure has occurredwithin the any one of the plurality of areas.
 9. The network managementserver according to claim 5, wherein the determination procedurecomprises setting, when the communication apparatus in which a failurehas occurred is detected within the any one of the plurality of areas,in a case where an alternative path that avoids passing through thecommunication apparatus in which the failure has occurred within the anyone of the plurality of areas is settable for the transmission path, thealternative path for the any one of the plurality of areas, anddetermining that the any one of the plurality of areas does notcorrespond to the failure occurrence area.
 10. A network managementserver to be coupled to area management servers for managing respectiveareas of an area group forming a network, the network management servercomprising: a processor for executing a program; a memory for storingthe program to be executed by the processor; an interface forcontrolling communications to/from each of the area managing servers;and a storage for storing data, wherein: the storage stores, in terms ofa transmission path within the network, for each occurrence pattern of afailure occurrence area in which a failure has occurred in thecommunication apparatus among a plurality of areas through which thetransmission path passes: information for identifying a recovery planeserving as a set of recovery paths corresponding to the each occurrencepattern; and information for identifying the communication apparatusthrough which each of the recovery paths passes, in association witheach other; the area managing servers each store recovery informationcomprising: information for identifying the recovery plane serving asthe set of recovery paths passing through a communication apparatuswithin an own area; and information for designating couplingcounterparts to which the communication apparatus within the own area isto be coupled in each of the recovery paths passing through thecommunication apparatus within the own area; and the network managementserver executes: an identification procedure of identifying, when afailure occurs in any one of the plurality of areas, whether or not thefailure corresponds to any one of failure occurrence patterns; anacquisition procedure of acquiring the information for identifying therecovery plane corresponding to the one of failure occurrence patternsidentified in the identification procedure from the storage; and anotification procedure of notifying the area management server for anarea through which each of the recovery paths included in the recoveryplane passes of the information for identifying the recovery planeacquired in the acquisition procedure.
 11. The network management serveraccording to claim 10, wherein the notification procedure comprisesnotifying of the information for identifying the same recovery plane.12. The network management server according to claim 10, wherein: thenetwork management server executes a transmission procedure oftransmitting, to each of the area management servers, the recoveryinformation on the recovery path passing through the communicationapparatus within an area managed by the each of the area managementservers; and the identification procedure comprises identifying whetheror not the failure corresponds to any one of the failure occurrencepatterns after execution of the transmission procedure.
 13. The networkmanagement server according to claim 12, wherein: the network managementserver executes: a calculation procedure of calculating the recoverypaths corresponding to the occurrence pattern; and a generationprocedure of generating the information for designating the couplingcounterparts to which the communication apparatus through which each ofthe recovery paths calculated in the calculation procedure passes is tobe coupled; and the transmission procedure comprises transmitting therecovery information comprising the information for designating thecoupling counterparts generated in the generation procedure.
 14. Thenetwork management server according to claim 10, wherein: the networkmanagement server executes a determination procedure of determining,based on the failure that has occurred in the communication apparatuswithin any one of the plurality of areas, whether or not the any one ofplurality of areas corresponds to the failure occurrence area in whichthe communications are disabled; and the identification procedurecomprises identifying whether or not the failure corresponds to any oneof the failure occurrence patterns based on a determination resultdetermined in the determination procedure.
 15. A recovery method to beexecuted by a network management server to be coupled to communicationapparatus within respective areas of an area group forming a network,the network management server comprising: a processor for executing aprogram; a memory for storing the program to be executed by theprocessor; an interface for controlling communications to/from thecommunication apparatus; and a storage for storing data, the storagestoring, in terms of a transmission path within the network, for eachoccurrence pattern of a failure occurrence area in which a failure hasoccurred in the communication apparatus among a plurality of areasthrough which the transmission path passes: information for identifyinga recovery plane serving as a set of recovery paths corresponding to theeach occurrence pattern; and information for identifying thecommunication apparatus through which each of the recovery paths passes,in association with each other, the communication apparatus each storingrecovery information comprising: information for identifying therecovery plane serving as the set of recovery paths passing through anown apparatus; and information for designating coupling counterparts towhich the own apparatus is to be coupled in each of the recovery pathspassing through the own apparatus, the recovery method comprisingexecuting, by the network management server: an identification procedureof identifying, when a failure occurs in any one of the plurality ofareas, whether or not the failure corresponds to any one of failureoccurrence patterns; an acquisition procedure of acquiring theinformation for identifying the recovery plane corresponding to the oneof failure occurrence patterns identified in the identificationprocedure from the storage; and a notification procedure of notifyingthe communication apparatus through which each of the recovery pathsincluded in the recovery plane passes of the information for identifyingthe recovery plane acquired in the acquisition procedure.